This invention relates to a process for preventing odor in a polyorganosiloxane. More particularly, the present invention relates to process for preventing odor in a polyoxyalkylene group-containing polyorganosiloxane which is used mainly as an additive in cosmetic compositions to impart thereto gloss, spread, smoothness, softness, and the like.
A liquid polyoxyalkylene group-containing polyorganosiloxane which is conventionally called a polyether-modified silicone fluid features excellent solubility in water and alcohol as well as excellent affinity for water, so that it has utility in a wide variety of industrial fields as an additive, for example, for cosmetic compositions, perfumery, and toiletries such as shampoo and hand cream. Among these fields of application, especially in the field of cosmetics, the liquid polyoxyalkylene group-containing polyorganosiloxane exhibits prominent versatility as an additive for imparting gloss, smoothness, softness, and the like, which are characteristic of a silicone.
The polyorganosiloxanes have such usefulness, however, have the following drawback. Namely, the polyoxyalkylene portion of the silicon is susceptible to oxidation, so that it is impossible to avoid odors caused by rancidity with the lapse of time. Moreover, in the production of the polyoxyalkylene group-containing polyorganosiloxane a polyoxyalkylene and a polyorganosiloxane are heated to form a copolymer, but in this case, oxidation of the polyoxyalkylene chain with air in the reactants also occurs concurrently, giving the product a faint rancid smell even just after production.
In recent years, because consumer's preferences for cosmetics are diverse and slightly perfuming cosmetics are preferred, as a matter of course, odorless or extremely low-odor materials are required for cosmetic preparations.
In reply to this requirement, a variety of studies and developments have been made and the following processes are known at present.
First, methods which are generally practices include, for example, a process in which an adsorbent such as active carbon or clay is used, and a process in which deodorization is performed by steam distillation in a deodorizing kettle, but these processes have the problem that although the product can be made low-odor just after the deodorization treatment, it is difficult to control subsequent odors due to rancidity with the lapse of time. Further, a process in which a phenolic compound is added as an antioxidant is known, but this process has a problem with respect to human safety.
Next, Japanese Patent Publication No. 41210/1980 discloses a process for preventing odors from a polyorganosiloxane, especially a water-soluble polyorganosiloxane due to rancidity with the lapse of time, which process comprises adding tocopherol, which is well known as Vitamin E. Although this process has no problem with respect to human safety, it has problems, for example, limited use, because the resulting cosmetics are colored owing to the marked coloring property of tocopherol. Thus the compound cannot satisfy a requirement of colorlessness or light color when it is used in cosmetics and, further, the cost of such cosmetics would be high since tocopherol itself is an extremely expensive material.